/**
 * ***************************************************************************** Copyright (c) 2000,
 * 2010 IBM Corporation and others. All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0 which accompanies this
 * distribution, and is available at http://www.eclipse.org/legal/epl-v10.html
 *
 * <p>Contributors: IBM Corporation - initial API and implementation
 * *****************************************************************************
 */
package org.eclipse.ltk.core.refactoring.participants;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.OperationCanceledException;
import org.eclipse.core.runtime.PlatformObject;
import org.eclipse.ltk.core.refactoring.Change;
import org.eclipse.ltk.core.refactoring.RefactoringStatus;

/**
 * An abstract base class defining the protocol between a refactoring and its associated processor.
 * The API is very similar to the one of a {@link org.eclipse.ltk.core.refactoring.Refactoring}.
 * Implementors of this class should therefore study the interface of the refactoring class as well.
 *
 * <p>A refactoring processor is responsible for:
 *
 * <ul>
 *   <li>refactoring the actual element. For example if a rename Java method refactoring is executed
 *       its associated processor provides the precondition checking for renaming a method and
 *       creates the change object describing the workspace modifications. This change object
 *       contains elementary changes to rename the Java method and to update all call sides of this
 *       method as well.
 *   <li>loading all participants that want to participate in the refactoring. For example a Java
 *       method rename processor is responsible to load all participants that want to participate in
 *       a Java method rename.
 * </ul>
 *
 * <p>A refactoring processor can not assume that all resources are saved before any methods are
 * called on it. Therefore a processor must be able to deal with unsaved resources.
 *
 * <p>This class should be subclassed by clients wishing to provide special refactoring processors.
 *
 * @since 3.0
 */
public abstract class RefactoringProcessor extends PlatformObject {

  private ProcessorBasedRefactoring fRefactoring;

  /**
   * Set the owning refactoring.
   *
   * @param refactoring the refactoring
   * @since 3.1
   */
  /* package */ void setRefactoring(ProcessorBasedRefactoring refactoring) {
    Assert.isTrue(fRefactoring == null, "The refactoring can only be set once"); // $NON-NLS-1$
    Assert.isNotNull(refactoring);
    fRefactoring = refactoring;
  }

  /**
   * Returns the associated refactoring. Returns <code>null</code> if the processor isn't associated
   * with a refactoring yet.
   *
   * @return the associated refactoring
   * @since 3.1
   */
  public ProcessorBasedRefactoring getRefactoring() {
    return fRefactoring;
  }

  /**
   * Returns an array containing the elements to be refactored. The concrete type of the elements
   * depend on the concrete refactoring processor. For example a processor responsible for renaming
   * Java methods returns the method to be renamed via this call.
   *
   * @return an array containing the elements to be refactored
   */
  public abstract Object[] getElements();

  /**
   * Returns the unique identifier of the refactoring processor. The identifier must not be <code>
   * null</code>.
   *
   * @return a unique identifier.
   */
  public abstract String getIdentifier();

  /**
   * Returns a human readable name. The name will be displayed to users. The name must not be <code>
   * null</code>.
   *
   * @return a human readable name
   */
  public abstract String getProcessorName();

  /**
   * Checks whether the processor is applicable to the elements to be refactored or not. If <code>
   *  false</code> is returned the processor is interpreted to be unusable.
   *
   * @return <code>true</code> if the processor is applicable to the elements; otherwise <code>false
   *     </code> is returned.
   * @throws CoreException is the test fails. The processor is treated as unusable if this method
   *     throws an exception
   */
  public abstract boolean isApplicable() throws CoreException;

  /**
   * Checks some initial conditions based on the element to be refactored.
   *
   * <p>The refactoring using this processor is considered as not being executable if the returned
   * status has the severity of <code>RefactoringStatus#FATAL</code>.
   *
   * <p>This method can be called more than once.
   *
   * @param pm a progress monitor to report progress. Although availability checks are supposed to
   *     execute fast, there can be certain situations where progress reporting is necessary. For
   *     example rebuilding a corrupted index may report progress.
   * @return a refactoring status. If the status is <code>RefactoringStatus#FATAL</code> the
   *     refactoring is considered as not being executable.
   * @throws CoreException if an exception occurred during initial condition checking. If this
   *     happens, the initial condition checking is interpreted as failed.
   * @throws OperationCanceledException if the condition checking got canceled
   * @see org.eclipse.ltk.core.refactoring.Refactoring#checkInitialConditions(IProgressMonitor)
   * @see RefactoringStatus#FATAL
   */
  public abstract RefactoringStatus checkInitialConditions(IProgressMonitor pm)
      throws CoreException, OperationCanceledException;

  /**
   * Checks the final conditions based on the element to be refactored.
   *
   * <p>The refactoring using this processor is considered as not being executable if the returned
   * status has the severity of <code>RefactoringStatus#FATAL</code>.
   *
   * <p>This method can be called more than once.
   *
   * @param pm a progress monitor to report progress
   * @param context a condition checking context to collect shared condition checks
   * @return a refactoring status. If the status is <code>RefactoringStatus#FATAL</code> the
   *     refactoring is considered as not being executable.
   * @throws CoreException if an exception occurred during final condition checking. If this
   *     happens, the final condition checking is interpreted as failed.
   * @throws OperationCanceledException if the condition checking got canceled
   * @see org.eclipse.ltk.core.refactoring.Refactoring#checkFinalConditions(IProgressMonitor)
   * @see RefactoringStatus#FATAL
   */
  public abstract RefactoringStatus checkFinalConditions(
      IProgressMonitor pm, CheckConditionsContext context)
      throws CoreException, OperationCanceledException;

  /**
   * Creates a {@link Change} object describing the workspace modifications the processor
   * contributes to the overall refactoring.
   *
   * @param pm a progress monitor to report progress
   * @return the change representing the workspace modifications of the processor
   * @throws CoreException if an error occurred while creating the change
   * @throws OperationCanceledException if the condition checking got canceled
   * @see org.eclipse.ltk.core.refactoring.Refactoring#createChange(IProgressMonitor)
   */
  public abstract Change createChange(IProgressMonitor pm)
      throws CoreException, OperationCanceledException;

  /**
   * Additional hook allowing processors to add changes to the set of workspace modifications after
   * all participant changes have been created.
   *
   * @param participantChanges an array containing the changes created by the participants
   * @param pm a progress monitor to report progress
   * @return change representing additional workspace modifications, or <code>null</code>
   * @throws CoreException if an error occurred while creating the post change
   * @throws OperationCanceledException if the condition checking got canceled
   * @see #createChange(IProgressMonitor)
   */
  public Change postCreateChange(Change[] participantChanges, IProgressMonitor pm)
      throws CoreException, OperationCanceledException {
    return null;
  }

  /**
   * Returns the array of participants. It is up to the implementor of a concrete processor to
   * define which participants are loaded. In general, three different kinds of participants can be
   * distinguished:
   *
   * <ul>
   *   <li>participants listening to the processed refactoring itself. For example if a Java field
   *       gets renamed all participants listening to Java field renames should be added via this
   *       hook.
   *   <li>participants listening to changes of derived elements. For example if a Java field gets
   *       renamed corresponding setter and getters methods are renamed as well. The setter and
   *       getter methods are considered as derived elements and the corresponding participants
   *       should be added via this hook.
   *   <li>participants listening to changes of a domain model different than the one that gets
   *       manipulated, but changed as a "side effect" of the refactoring. For example, renaming a
   *       package moves all its files to a different folder. If the package contains a HTML file
   *       then the rename package processor is supposed to load all move HTML file participants via
   *       this hook.
   * </ul>
   *
   * <p>Implementors are responsible to initialize the created participants with the right
   * arguments. The method is called after {@link #checkFinalConditions(IProgressMonitor,
   * CheckConditionsContext)}has been called on the processor itself.
   *
   * @param status a refactoring status to report status if problems occur while loading the
   *     participants
   * @param sharedParticipants a list of sharable participants. Implementors of this method can
   *     simply pass this instance to the corresponding participant loading methods defined in
   *     {@link ParticipantManager}.
   * @return an array of participants or <code>null</code> or an empty array if no participants are
   *     loaded
   * @throws CoreException if creating or loading of the participants failed
   * @see ISharableParticipant
   */
  public abstract RefactoringParticipant[] loadParticipants(
      RefactoringStatus status, SharableParticipants sharedParticipants) throws CoreException;
}
